Clinical utility of newly developed immunoassays for serum concentrations of adalimumab and anti-adalimumab antibodies in patients with Crohn's disease.

BACKGROUND/AIM: The appearance of anti-adalimumab antibodies (AAAs) is associated with low serum adalimumab (ADA) trough levels and a decrease of clinical response. The goal of this study was to assess the accuracy and clinical utility of new immunoassays for serum ADA and AAA levels.

PATIENTS AND METHODS: Serum ADA trough levels and AAA levels were measured using new immunoassays in 40 patients with Crohn's disease (CD) receiving ADA maintenance therapy.

RESULTS: Serum ADA trough levels were 12.3 ± 9.6 μg/ml (n = 40) in CD patients, and 14 of 40 patients (35 %) were positive for AAAs. A negative correlation was observed between serum AAA levels and ADA trough levels (y = -6.02x + 18.7, r = -0.54, P < 0.001, n = 40). The ROC (receiver-operator curve) analyses indicated that an ADA trough of 5.9 μg/ml was optimal to maintain negative CRP (C-reactive protein) levels (≤0.3 mg/dl). The ADA trough levels were significantly lower in patients positive for AAAs (5.5 ± 5.4 μg/ml, n = 14) than in patients negative for AAAs (16.0 ± 9.5 μg/ml, n = 26). The CRP and ESR levels were significantly higher in AAA-positive patients than in AAA-negative patients. Serum albumin levels were significantly lower in AAA-positive patients. The positive rate for AAAs in patients who lost a response to infliximab (50 %) was significantly higher than that of anti-TNF-α drug naïve patients (12.5 %).

CONCLUSIONS: These new assays for serum AAA trough and AAA levels are useful for routine clinical use and may help guide selection of optimal management strategies for IBD patients with a loss of response to ADA.